Continuously variable transmissions (CVT's) are transmissions that change gear continuously, not in discrete intervals. This continuous nature of CVT's gives them an infinite number of gear ratios, making them very attractive for automotive use. One attractive aspect is that higher efficiency of the engine may result because the engine can be run at a desired speed for a broad range of vehicle speeds, allowing an efficient engine operating point for the specific power requirement.
The control of an engine-CVT drivetrain should take into account the desired drivetrain fuel efficiency as well as the desired drivetrain performance. Prior drivetrain controls have either provided improved fuel efficiency at the expense of performance or improved performance at the expense of fuel efficiency.